In organic EL (electroluminescence) lighting panels used for organic EL lighting devices, generally, transparent electrodes formed of transparent conductive materials such as ITO, ZnO, SnO2 (NESA glass), and the like are used as electrodes at the side where the light is led out. Since the volume resistivities of the above-described transparent conductive materials are high, the sheet resistances become high in the case where the materials are used as thin films. Therefore, in an organic EL lighting panel using the above-described transparent electrode, a voltage drop due to increase in wiring resistance is caused as distanced from a transparent electrode end (feed terminal from power supply), i.e., as approached toward the inside (center) of the organic EL lighting panel. When the voltage drops at an electrode part, it causes an electric power loss at the electrode part as well as decreases in luminance and chromaticity, and thereby the luminance uniformity and chromaticity uniformity within a surface of an organic EL lighting panel are decreased. The above-described decreases in luminance and chromaticity are caused because an organic EL element is an electroluminescent type element, an electric field at the center of the element becomes smaller than that at the vicinity of a feed terminal because of a voltage drop, the injection efficiency of a carrier (hole/electron) is decreased, and the luminous efficiency is decreased.
Hence, for reducing the wiring resistance at the transparent electrode side, the provision of an auxiliary electrode on a transparent electrode has been considered (see, for example, Patent Documents 1 and 2). At this time, an end-insulating layer for covering the end of the transparent electrode is provided for avoiding the conduction between an upper electrode (in the case where the transparent electrode is an anode, a cathode) provided at the upper side relative to a translucent substrate and a transparent electrode, and an interlayer-insulating layer for covering the auxiliary electrode is provided for avoiding the conduction between the auxiliary electrode and an organic EL element (see, for example, Patent Document 2).
The organic EL lighting panel is manufactured, as shown in FIGS. 9A to C, by the following steps, for example. A translucent electrode material (for example, ITO) is laminated (formed) on a translucent substrate and the patterning using a photoresist is performed to form a translucent electrode layer. After removing the photoresist, an auxiliary electrode-forming material layer is formed, and an auxiliary electrode of a desired pattern is formed by a photolithography step or the like. Specifically, an auxiliary electrode-forming material layer is laminated all over a translucent substrate on which a translucent electrode layer is formed, a photoresist is applied thereto, the auxiliary electrode-forming material layer is formed into a desired pattern by an exposure through a mask on which a desired pattern is formed, a development, and an etching, and thereafter the resist on the auxiliary electrode-forming material layer is removed. Thereafter, an interlayer-insulating layer for covering the auxiliary electrode and an end-insulating layer for the end of the translucent electrode layer are each formed by a photolithography step in the same manner as described above. Then, an organic layer and an upper electrode layer are laminated thereon to manufacture an organic EL lighting panel.